CHEMICALS.

Nitrate of Silver in Crystals.

M. Nitrate of Ammonia.

M.S. Pure Potash, prepared by Alcohol.

M. White Sugar Candy.

M. Tartaric Acid.

Alcohol.

D.S. Liquor Ammonite.

S. Sugar of Milk.

D. Tartrate of Soda and Potash (Rochelle Salts).

Distilled Water.

Nitric Acid.

Pitch.

Fine Rouge.

Turpentine.

All the above chemicals should be as pure as possible, especially the potash. They are not all required in each process to be described, those specially used are therefore marked, M., D., S. These letters indicate the three processes, called respectively, Martin’s, Draper’s, and the Sugar of Milk. The method of preparing, cleansing, and immersing the mirror, and polishing the silver film, is the same in all processes.

To support the Mirror in the Silvering Vessel.

There are several ways of doing this, dependent on the depth of the vessel. Should the back of the mirror be level with the edge of the dish, when its face is the requisite distance, (about )^-inch) from the bottom, it may be secured as follows Procure a strip of wood, about three inches wide, and of sufficient length to rest securely on the opposite sides of the vessel. Pour on the centre of this piece of wood some melted pitch, and whilst it is still hot, place it on the back of the mirror, previously smeared very slightly with turpentine, which should be allowed nearly to evaporate. The turpentine will secure the adhesion of the hot pitch to the glass, and care should be taken that, when cold, the mirror and its support are firmly cemented together before commencing the silvering process. Should the dish be so deep that there would be more than the requisite distance between the bottom of it and the face of the mirror, a block of wood of sufficient thickness must be screwed to the suspending strip, and the speculum cemented to it, instead of directly to the strip itself. On the contrary, should the dish be very shallow, the mirror may be raised, by placing thin pieces of wood between the strip and the edges of the dish; or the strip need not rest on the edges of dish, but have an independent support at each end. When the speculum

---

Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,53 %.

La langue de reconnaissance de l'OCR est l'Anglais.

---